#!/usr/bin/env bash
#
# resolve-spf-ips.sh
# ------------------
# Holt alle ip4:/ip6:-Einträge aus dem SPF-TXT-Record
# einer Domain (z.B. spf.crsend.com).
#
# Usage:
#   resolve-spf-ips.sh spf.crsend.com

set -e

DOMAIN="$1"

if [[ -z "$DOMAIN" ]]; then
    echo "Usage: $0 <domain>" >&2
    exit 1
fi

dig +short TXT "$DOMAIN" \
  | tr -d '"' \
  | sed -n 's/.*v=spf1 //p' \
  | tr ' ' '\n' \
  | grep -E '^(ip4|ip6):' \
  | sed -E 's/^ip[46]://' \
  | sort -u